• Microevolution happens at the population level (review)

• Macroevolution: Speciation events form evolutionary independent populations
  • whole taxonomic groups

• New species are the bridge between evolution within a population and large patterns in evolution

• Textbooks: A group of populations whose members have the potential to interbreed in nature and produce viable offspring

• Textbooks: A group of populations whose members have the potential to interbreed in nature and produce viable offspring

• Reproductive isolation between populations results in a lack of gene flow
  • gene flow:

• Individuals do not interbred with other populations or are unable to produce viable offspring after mating
  • pre- and post-zygotic

• BSC: Members of a biological species are united by the potential ability to be reproductively compatible

• How do we effectively evaluate isolation?
  • Is this even possible in fossils?

• Geographic proximity: how do we know if they cant make babies?

• Asexual reproduction
  • Belloid rotifers haven’t reproduced sexually for > 80 million years
  • An estimated 2000 species of asexual rotifers are known

• Can do with all organisms but…. what kinds of traits & how many?

• Species can change their form: Polymorphisms

• Cryptic species that do not differ in morphology (e.g., fossil shells)

• Subjective to the scientist!

• Three spine stickleback fish rapidly evolve
  • moved from oceans to freshwater when glaciers retreated

• Freshwater habitats brought new selection pressures
  • variety of habitats
  • new resources
  • change in competition

• Molecular biology examined each speciation
  • ocean → fresh: one gene with bony armor plate
  • fresh habitats → many genes based on selection pressures